This invention relates to an improved system for storing items while they are being sterilized, while they are being stored awaiting use, while they are in the process of being used, and after they have been used and are awaiting resterilization. The system is particularly useful in connection with the sterilization and storage of medical items, such as surgical instruments.
The most commonly used method for sterilizing surgical instruments and other medical items is to place them in towels which are enclosed in a sheet and taped shut for placing in a sterilizing autoclave. Sterilizing steam applied to the interior of the autoclave penetrates the porous materials surrounding the items to be sterilized. Moisture is removed by a vacuum drying cycle within a vacuum autoclave. When pressure is then returned to normal by admitting room air, unsterile air and lint from the towels are drawn into the center of the package. When the package is removed from the autoclave and cooled, additional room air circulates into the package. Thus, the items are immediately contaminated to some extent. If the package is not used immediately and placed in storage for a period of time, it must be returned to the autoclave for resterilization. It is estimated that two-thirds of sterilization work load in many hospitals is for items that were not used within the shelf life of the pack. This of course is an expensive and inefficient procedure which adds to the skyrocketing costs of medical treatment. Thus, a need exists for a practical and reliable system for handling sterile items and for maintaining sterility.
Some attempts have been made to improve the system for sterilizing medical items. However, all have fallen short of the mark such that the old approach of wrapping items in towels is still the method most widely used. U.S. Pat. No. 3,697,223--Kovalcik discloses a container in which items are to be sterilized and stored. However, the container is not adequately sealed after sterilization. U.S. Pat. No. 2,997,397--Doulgheridis and an earlier U.S. Pat. No. 2,092,445 of the same patentee disclose containers primarily for sterilizing food but are also said to be useful for surgical items. In those patents a vacuum is applied to a container which is open to initially withdraw the atmosphere within it, steam is applied, and the temperature of the stem melts a solder plug allowing a valve or cover for the container to close. Thus, the container is closed while still within the sterilizing environment but the sterilizing steam is trapped within it. This steam condenses in the container when cooled and is particularly undesirable for items which would be dry, such as surgical bandages.
U.S. Pat. No. 3,468,471 discloses a bag for containing items to be sterilized wherein the bag is porous at steam temperatures to permit steam to be applied to the contents of the bag but is not porous at lower temperatures. The bag also includes a temperature responsive valve which is open when the bag is in the autoclave so as to permit the steam to be rapidly withdrawn from the bag when a final vacuum is applied in the autoclave cycle. This valve closes to seal the container but not until the bag is removed from the autoclave and the temperature is dropped sufficiently to solidify an adhesive material. Thus, the bag is exposed to unsterile environment before being sealed. There are other patents dealing with the sterilization of food wherein a container is sealed in a sterile environment; however, steam or other atmosphere is deliberately maintained within the container and such arrangements are not suitable for medical items. Moreover, such containers are not automatically sealed in response to conditions of the environment surrounding the container.
Thus, a need still exists for a practical, easy to operate container useful for medical items, as well as other products, while such items are being sterilized, stored or used. Further, a need exists for such a container wherein maximum sterilization is obtained employing currently used autoclave apparatus. This is, of course, of vital importance for minimizing infections and other such medical problems encountered during surgury and post operative recovery. The present invention satisfies such need by providing maximum sterility consistent with that available by present-day autoclaves. Further, the system is practical and easy to operate by unskilled personnel, and current evidence indicates that it can greatly reduce the cost of sterilizing medical items in hospitals, doctors offices and other facilities employing autoclaves.
In accordance with the present invention, the items to be sterilized are placed within a container; and a sterilizing gaseous environment, such as high pressure steam, is applied to the container exterior, with the exterior in communication with the interior, for a period of time sufficiently long to sterilize the container and its contents. The application of the sterilizing environment is then discontinued and the pressure on the exterior of the container is reduced to allow the environment with the container to be withdrawn or escape from the container. The sterilized container is automatically sealed by means responsive to the environment surrounding the container so as to prevent fluid flow into the container before allowing the container to be exposed to an unsterilized environment.
Thus, when the container is placed within a vacuum autoclave, the container is open during the high pressure steaming operation, following which the steam is withdrawn by a final vacuum, and the container is automatically sealed while it is still within the autoclave and before unsterile exterior air is allowed to enter the autoclave. Thus, when the container is removed from the autoclave, its contents are sealed within a dry, essentially atmosphere-free container. With suitable material and gasketing, the container will remain in this condition for a long period of time in storage. The container contents remain sterile and air does not enter the container until it is opened in the operating room where the contents are to be used. Thus, exposure to unsterile environment is kept to an absolute minimum. The existence of the vacuum within the container of course produces a sound when the pressure is equalized and this gives the user assurance that the container was still sealed.
When the container is used in a non-vacuum (so-called gravity type) autoclave, most of the sterilizing steam escapes from the container when the steam phase is interrupted and the pressure is allowed to drop to room pressure. Some water vapor remains in the container at that time but the amount is quite small. When the container is sealed, and the temperature within the container drops to ambient temperature, this small amount of vapor condenses creating a relatively high vacuum within the container. This condensate can be accommodated by a quantity of dessicant to minimize the effect on the container contents. While use of the container in a vacuum type autoclave is preferable, there are a large number of the gravity type autoclaves in use and the system described provides the best sterility possible with such equipment.
In one form of the container, a valve is provided in a container wall which is normally closed but opens in response to steam temperatures so that steam applied to the exterior of the container can enter the container. After the steaming phase of the autoclave cycle and a reduction in temperature, the valve will once more automatically close, while the container is still within the autoclave and before room air is admitted to the autoclave. In addition, the valve is pressure responsive to act as a check valve so that when the pressure on the interior of the container exceeds that on the exterior, the valve will open but the valve will prevent flow into the container. Thus, in a vacuum autoclave, the sterilizing steam can be exhausted through the valve even after the valve has been initially closed by the drop in temperature which occurred when the steaming phase is completed. In one such arrangement, a bimetallic spring loaded valve is utilized which is both temperature responsive and pressure responsive.
In another arrangement disclosed herein, a valve remains open until near the end of a sterilizing cycle and is then closed in response to the falling pressure at the end of the sterilizing cycle. The closing means is triggered by an earlier rise in the temperature when steam is applied. This arrangement is claimed more specifically in a co-pending U.S.A. patent application, Ser. No. 821,042, filed Aug, 1, 1977.
An advantage of the arrangements disclosed is that the automatic operation of the closing of the container is independent of the duration of the sterilizing phase of a cycle. Thus, the containers remain open during this sterilizing to insure adequate sterilizing. This is particularly important with loads having considerable mass that must be heated to sterilizing temperatures. With loads of considerable mass, such as a quantity of medical instruments, there may be condensation of steam when it strikes the cooler instruments. To make certain that the condensate is not trapped within the container, the valve may be located at the bottom of the container to permit drainage until the valve is closed after the sterilizing phase is completed.